These are designed and manufactured with high grade materials. Bushes are precisely machined to house bearing 23024 for flute roller. This set includes 2 pair (4 pcs) of (casting iron) bushes . (4pcs of 23024 NSK/SFK Bearings) (4pcs) High Chromium High Carbon steel sliding Plates ( which helps bushes to move on slides ). Nip Adjustment (worm screw) for flute rolls and (4 pcs of hardchrome bush plates)